When piloting an aircraft, avoidance of collisions is always of significant concern. Even pilots of private and commercial flights are taught to be highly vigilant with regard to both terrestrial hazards, such as mountains and broadcast towers, as well as airborne hazards such as other commercial and private aircraft, hot air balloons, etc. In addition to pilot vigilance, air traffic control specialists and highly sophisticated radar-aware software systems monitor and communicate with aircraft when they are located in high traffic areas, so as to provide further protection against collisions.
Of course, the problem of collision avoidance is much more severe in air combat situations, where aircraft speeds are much greater, aircraft typically fly in closely-spaced groups, and it is sometimes necessary for individual aircraft to make rapid, unplanned maneuvers, for example when avoiding hostile ground or air fire and/or when pursuing hostile aircraft. Under such circumstances, strong demands are placed on a pilot's attention and concentration, such that even highly skilled and trained pilots run the risk of colliding with terrestrial hazards or with other, friendly aircraft.
Various approaches have been proposed and/or implemented with regard to automatically detecting and avoiding potential collisions of aircraft with terrestrial and/or airborne hazards. These typically include an aircraft scanning the environment using RADAR or a similar method, and attempting to determine directions and relative distances to potential hazards. While this approach can be effective for avoiding hazards that are somewhat distant, which is typically the case for terrestrial threats and hostile air threats, this approach can be insufficient for avoiding collisions with friendly aircraft, which may be located very nearby, typically closer than 10 nautical miles (Nm).
One approach to avoiding collisions between friendly aircraft is to equip each of the aircraft with a special transponder, such that the aircraft can exchange location, speed, and direction information with each other. Examples include the civilian “Traffic collision avoidance system” (TCAS), and the military “Airborne collision avoidance system” (ACAS). Of course, for use in combat environments the transponder communications must be highly resistant to jamming, spoofing, and other hostile interference.
More recently, the United States Air Force has begun testing the Auto-ICAS (Automatic Integrated Collision Avoidance System), which combines RADAR-based capabilities with exchange of messages between friendly aircraft so as to avoid both friendly and hostile air collisions as well as collisions with terrestrial hazards. With regard to avoidance of collisions between friendly aircraft, the Auto-ICAS specification requires that the system must include a datalink that enables message exchanges of 768 bits each at a rate of 20 Hz between up to 10 aircraft that are located within a 10 Nm range of each other.
While real time exchange of location, speed, direction, and other relevant information can be effective in avoiding collisions between friendly aircraft flying within 10 Nm of each other, the implementations that have been proposed all require that participating aircraft be equipped with special transponders that are dedicated to the collision avoidance system, which leads to a significant increase in “space, weight, power, and cost” (SWaP-C).
What is needed, therefore, is a system and method of avoiding collisions between friendly aircraft in a combat situation that meets the Auto-ICAS specification while minimizing consumption of space, weight, power, and cost.